Attempt to Use a TEG to Charge a Phone

The desire was to build a TEG power generator so it could charge my phone while camping. Having previously experimented with a 40mm TEG, I figured a larger (60mm by 60mm) TEG module would generate more power as it has more than twice the surface area. Cooling would be done using a liquid heat exchange block. Heat would come from a small camp stove.

Sometimes you just know a project isn't going to deliver the results you hope for, yet you persist to see how far short it will fall. After ordering the components, I watched some you tube clips on the subject, it became more and more apparent that the power generated would be insufficient to charge a phone. Let's see how far short it will fall.

TGM-199-2.0-1.2 TEG (60mm by 60mm)

Water-cooled Exchanger

Heat exchange paste

60mm by 3mm Aluminum bar (100mm long)

Plastic tubing

A heat source

A water source

Temperature gun (for testing)

Multimeter (for testing)

2, 20-liter camping water containers

5-volt power converter

Flow through USB power meter

My original idea was to use a pellet fuel stove to provide heat to the TEG. I had thought that if the TEG module was mounted on an aluminum bar, heat going to it could be controlled by sliding the bar. The nearer the TEG was to the flames the hotter it would get. I used a temperature gun to measure how hot different places on the bar got over the flames - the temperature appeared to it vary dramatically, sometimes reading 200c then up to 500c. This could easily cause the TEG to overheat and fail.

A camping gas stove was then tried. The reading looked more constant with the bar reading 200c when over the flames of the burner but then the bar started to bend, indicating the temperature was much higher than that being shown. A more stable and easier to control heat source was required for testing. Tea candles were investigated as a heat source, but it was observed they wouldn't be putting out enough heat.

It was decided, for testing purposes, a fry pan on a kitchen stove would be used to prove a controlled heat source.

A 20cm length of 60mm by 3mm aluminum bar was cut with a hacksaw. Heat paste applied to the middle of the bar and a then a 60mm-by-60mm TEG placed on top. Heat paste was then applied to the top of the TEG and a 80mm by 80mm Liquid heat exchange block place on top. An eight Kg weight was place on top to help make a good join while the paste/adhesive set. Some days later the length of the aluminum was cut to shorten it to about 10 cm in length so it could be placed on a frying pan for testing purposes.

Before heating up the TEG the cooling block was connected to a water source. I connected a hose to a tap for the inflow and the outflow was placed in my kitchen sink for testing purposes. Later, a portable cooling source will need to be devised.

I measured the heat of the frying pan using a temperature gun. The Volts and Amps being generator were measured with a multimeter. These were plotted on a graph to see how much power the TEG could generate.

It looks like 4 watts is generated at 200c. (3.2Volts,1.3 Amps). I got the impression at temperatures over 250c the chance of 'cooking' the TEG increased dramatically.

The heat source and water source were applied to the TEG for over an hour at a temperature of 200c delivering a steady output of 4 watts of electricity. These reading were taken while the TEG wasn't powering anything.

If a couple of these TEGS are used at a stable temperature of 200 - 220c with water flowing though the heat blocks, just maybe a phone could be charge. The next challenge is to come up with a steady heat source and water flow for use while camping.

Having tap water flow through the liquid cooling block prevented the TEG from overheating and allowed heat transfer resulting in electricity generation. But when camping you may not have a convenient water tap nearby and discarding the water is wasteful. Is it possible to have a 'closed loop' cooling cycle, where the water is reused for cooling?

A couple of 20-liter water containers were tried for cooling. One filled with cold water and positioned slightly higher than the frypan with the TEG and cooling block. The other empty container was positioned on the floor. Gravity and the syphon effect caused water to flow through the block. The surface of the cooling block was monitored as was how hot the hoses got. After most of the water had flown out of the higher container into the lower one, their positions were swapped over. It took about 15 minutes for all the water to flow into the lower container and the rate could be adjusted using the container taps. The water didn't heat up that much. A closed loop system for the cooling side of the TEG has been found which will work while camping.

Readings were taken by a Multimeter and graphed. This set up gave a steady 3.5 Watts of power over 90 minutes with a LED torch connected. The water tanks were swapped places about 6 times, but no new cold water was added, the water temperature had increased to 28c at the end. The surface temperature of aluminum heat exchange did not raise above 60c.

Having found a reliable way to cool the TEG, A reliable heat source needs to be sourced. A public BBQ at a camping ground was investigated. The temperate on its cooking surface varied but it looks like if the TEG was placed correctly, it could be used as a heat source.

A voltage booster was attached to increase the voltage to 5 volts. This was connected to a power flow though meter and connected to a rechargeable battery. It showed that the previous multimeter measurements were way off. Only about 200mA was being drawn, giving just under 1 watt of power. My hopes of being able to use this setup to charge a phone looked to be dashed. Unfortunately, I had already ordered a 2nd TEG to use in series with this one. Even together the power output is not going to be enough to practically recharge a phone in a reasonable amount of time.

The second TEG was tested by placing a 2nd water cooler block on top and connecting it in series to the first TEG. I didn't apply thermal adhesive as after the test I wanted to be able to use the TEG for another project. The voltage of the 2 TEGs was over 5 volts and together they were able to start charging a battery pack at just over 1 watt. After some more testing I found the battery pack would no longer draw a charge. While showing 5 volts, no amps or watts was being drawn, and the battery was not being recharged. All in all, not the outcome I was aiming for.

The advantage of a solar panel is that it can be set up and left to do its thing. I brought a portable solar charger and tried it out on a winter camping trip. During a bright winter's day, it was able to charge a 10Watt hr. battery 25% over 5 hours - enough to charge my phone by 60%. I expect during a bright summer's day it will fully recharge the battery and be a better way to recharge a phone than using a TEG.